Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!uunet!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: A2000 AUTOCONFIG (HELP)
Message-ID: <21385@cbmvax.commodore.com>
Date: 8 May 91 16:07:27 GMT
References: <1991May6.112803.8009@cc.curtin.edu.au>
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 35

In article <1991May6.112803.8009@cc.curtin.edu.au> tnewmanda@cc.curtin.edu.au writes:
>Can I please have some help with a Frame Grabber board for the Amiga 2000?
>The problem is as follows:
>I'm using the example circuit from the A2000 technical manual for the bus 
>interface. Having built and tried the circuit I'm unable to get it to work!

The autoconfiguration logic is pretty simple.  But you really don't want to
make exact copies of what's in the A500/A2000 Technical Reference Manual.
That's provided mainly for your education, so that you can see one practical
application of the general concepts in this book.

In any case, while it's been some time since I looked at this, my copy of
the manual seems to indicate that there are two bugs in the TESTRAM PAL on
page 43.  These are the correct versions of the equations:

	DBOE	= /RES * BDSEL * /BERR * /SHUTUP * /RD +
		  /RES * BDSEL * /BERR * /SHUTUP *  RD * ASQ

	CONOUT	= /RES * /ASQ * PRECON +
		  /RES * CONOUT

If you copied that DBOE equation verbatim, your problem was that the read
term (second and term) was looking for SHUTUP asserted rather than negated,
so you never turned data buffers on for reads.  That's why I recommend really
learning these equations; it would be an obvious problem if you looked it
over very carefully.  I realize that it's often hard to trust your judgement
over that of some authoritative reference.  But even authoritative references
ain't perfect.



-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
      "That's me in the corner, that's me in the spotlight" -R.E.M.